Previous observational studies have reported that heavy alcohol intake is a risk factor for hypertension. But such studies may be confounded by factors such as diet, smoking, exercise levels and socio-economic position. Clinical trials exploring the link are difficult to implement and have limited follow-up time.

However, a study at the U.K.’s University of Bristol, led by Dr Sarah Lewis of the Department of Social Medicine, took a different approach and focused on people who have a mutation in a gene that affects their body’s ability to eliminate alcohol.

The body initially metabolizes alcohol into an intermediate compound, acetaldehyde, which it further metabolizes and then eliminates from the body. The major enzyme responsible for this elimination is alcohol dehydrohenase 2 (ALDH2).

In some people, a genetic mutation leads to an inability to metabolize acetaldehyde and causes an accumulation of of it after alcohol intake. This mutation is common in some Asian populations and results in facial flushing after consumption of alcohol, coupled with intense nausea, drowsiness, headache and other unpleasant symptoms. People with this mutation therefore drink much less than those without it.

The researchers looked at the ALDH2 genotype, comparing the blood pressure of those who have this mutation – the *2 *2 genotype – with those who do not – the *1 *1 genotype.

The study found that individuals with the *1 *1 genotype, who had an alcohol intake of around 3 units per day, had strikingly higher blood pressure than those with the *2 *2 genotype, who tend to drink only very small amounts, or no alcohol.

Dr Lewis said: “This study shows that alcohol intake may increase blood pressure to a much greater extent, even among moderate drinkers, than previously thought. Large-scale replication studies are required to confirm this finding and to improve the precision of our estimates.”